1. Field of the Invention
This application relates to a CD-Audio system having electronic shock protection, and more specifically to a redistribution of functions involved in the electronic shock protection of the CD-Audio system.
2. Description of the Prior Art
Systems to reproduce audio signals from a Compact Disc (CD) are used in several conditions. Complete CD-Audio entertainment systems consist typically of a CD-Module and a host unit, which usually implements the Human Machine Interface (HMI). Many host units have also entertainment units implemented to reproduce compressed audio formats like MP3 or WMA from CD or other media (e.g. flash memory cards or USB-memory Sticks). Also navigation units are often implemented in the complete system. Such complex systems need memory resources for processing compressed audio decoding or calculations for navigation.
Especially in portable and automotive entertainment systems, a so-called Electronic Shock Protection (ESP) method is used to overcome reading problems produced by mechanical shocks. The ESP method normally uses a memory buffer to store the audio data before the data is presented to the speakers. The buffer is filled with audio data at higher speed than the audio data is presented to the speakers. When mechanical shocks happen to the system, the filling of the buffer stops but audio data for presentation is still available until the audio buffer is empty. During this time retries for reading new audio data from the CD are executed.
Two implementations for CD-Audio ESP-Systems are available in the market:
1. ESP-System is implemented completely in the CD-Module.
2. ESP-System is implemented completely in the host system.
In the first case, the disadvantage is that the ESP-Memory is assembled in the CD-Module and can be used for CD-Audio playback only. During playback of CD-Audio tracks, usually the memory resources of the host unit are not required and are wasted. On the other hand, when CD-Audio is not being reproduced, the ESP-memory in the CD-Module is not used and is wasted. This system is costly because of double assembled memory.
In the second case, the disadvantage is that the host needs a processor with high performance to detect erroneous data and for seamless connection of the incoming pieces of audio. Often performance and reliability problems are caused by insufficient host processor performance in these systems. Usually the host unit implements the ESP-system to overcome wasting of memory. In these applications, simple CD-Modules without any ESP functionalities are used. Also the fact that, for every single application, the ESP-system has to be implemented completely in the host, which increases development time and requires a lot of knowledge about different kind of CDs produced in the market.